Besides the bizzion tech blogs and twitter feeds which litter the internet, I find book publishers' email newsletters to be a good source of what is new and upcoming in the tech field.
The advantage of dead-tree publishers is that they take the time to see what is really viable and take a little longer term view than web-only sources.
A print publisher has more at stake if a book bombs - a warehouse full of unsold books.
A few that I subscribe to:
The Pragmatic Programmer newsletters and magazines.
Mannings subscribe to Newsletter.